There is a lighting device for vehicle which is provided with a socket, a light emitting unit which is provided at one end portion of the socket, and includes a light emitting diode (LED), and a power feeding terminal of which one end portion provided inside the socket is electrically connected to the light emitting unit.
Heat generated in the light emitting diode is mainly radiated to the outside through the socket. For this reason, the socket is formed of a material with high heat conductivity such as metal, or a high heat conductive resin. In this case, the material with high heat conductivity such as metal, or the high heat conductive resin has conductivity. For this reason, an insulating portion formed of a resin with an insulating property is provided between the socket and the power feeding terminal. The insulating portion is press-fitted into a hole provided in the socket.
Here, there is a difference in thermal expansion amount (or, thermal contraction amount) between the socket and the insulating portion which are formed of different materials. In addition, in a case of the lighting device for vehicle provided in a vehicle, a temperature in use environment is changed in a range of −40° C. to 85° C. For this reason, thermal expansion and thermal contraction of a different amount repeatedly occurs in the socket and the insulating portion due to the change in temperature of the use environment, and there is a concern that a sectional dimension of a hole into which the insulating portion is press-fitted may become large, or a sectional dimension of the insulating portion may become small. When a sectional dimension of the hole into which the insulating portion is press-fitted becomes large, or the sectional dimension of the insulating portion becomes small, there is a concern that a slight gap may be formed between the socket and the insulating portion, and bonding intensity therebetween may decrease.
Therefore, there is a desire for a development of a technology in which it is possible to improve reliability in fixing of the insulating portion.